Estimating the cost of predator avoidance in otariid seals

Aroa De Pietri

In the natural world life is all about a trade-off between costs and benefits. Avoiding predators through vigilance can be highly effective but can lead to a reduction in foraging opportunities and efficiency. Therefore, understanding the mechanisms animals use to avoid predation can prove insights into the predation level they threat and how this influences their activity patterns. However, investigating predator avoidance in free-ranging species is logistically difficult, particularly in cryptic marine mammals such as otariids. While the level of predation threat otariids face and the anti-predatory responses they adopt remain largely unknown, preliminary studies have suggested that otariids may use rolling behaviour in order to scan for potential predators within the water column. The findings of this study suggest that patterns in roll behaviour vary according to individuals’ body size and potential predator, rather than to their type of environment, and that the incorporation of such behaviour to otariids foraging trips implies additional energetic costs. However, even if this study suggests a relationship between roll behaviour and vigilance, it does not exclude the possibility of rolling being used by otariid seals as well for different purposes.